Control means for liquid fuel injection pumps



1955 x w. E. w. NICOLLS 2,698,614

CONTROL MEANS FOR LIQUID FUEL INJECTION PUMPS Filed April 24, 1953 Fig.2

Z12, v 'ezz/mz Fatentecl Jan. 4, 1955 three CONTROL MEANS FOR LIQUID FUEL INJECTION PUMPS Wilfrid Edward Walter Nicolls, Pinner, England,

to C. A. V. Limited, London, England assignor This invention relates to control means for liquid fuel injection pumps used on internal combustion engines, the control means being of the kind adapted to actuate the output-regulating member of the pump in response to the pressure existing in the air-intake manifold of the engine.

The object of the invention is to provide an improved control means adapted to ensure stability of action when the engine is running at an idling speed, or at high speed under a light load.

The invention comprises the combination of a hollow body part forming a chamber adapted for pipe connection with the engine air-intake manifold, a spring-loaded diaphragm (or piston) enclosing the open end of the body part and adapted for connection to the output-regulating member of the pump, an air-bleed valve comprising an axially slidable closure member operable by the said diaphragm (or piston), a seating member for the said closure member axially slidable in a bore in the end of the body part remote from the said diaphragm (or piston), and a second diaphragm (or piston) connected to the seating member and dividing a second chamber on the body part into two compartments, the arrangement being such that when the closure member is moved to its open position by the first diaphragm (or piston) a follow-up movement is imparted to the seating member by a differential air pressure acting on the second diaphragm (or piston).

In the accompanying drawings:

Figures 1 and 2 are sectional views respectively illustrating two embodiments of the invention.

Referring to Figure 1, there is provided a hollow body part 11 adapted to be mounted on the pump b. The open end of the body part is closed by a flexible loaded diaphragm c loaded by a spring a and adapted for attachment to one end of a slidable bar e serving (in known manner) to regulate the pump output. The said body part forms a chamber which is to be connected by a pipe g to a venturi throat in the air-intake manifold at the engine side of the throttle valve in the manifold.

At the other end of the said chamber is arranged an air-bleed valve. This comprises a seating member h which is axially slidable in a bore in the body part and has formed in it an axial bore which at the end remote from the diaphragm is adapted to form an annular seating for the head of a closure member i of the poppet type. The seating member h is attached to a second diaphragm k which divides another chamber in the body part into two compartments m, it one of which n contains the head of the closure member. These compartments are both open to the atmosphere through restricted orifices 0.

The stem 12 of the closure member extends through the seating member and into the first mentioned chamber 1, so that it can be moved to its open position by, and after a predetermined movement has been given to, the first mentioned diaphragm c. The closure member is normally held in its closed position by a spring j which serves also to press the diaphragm k, or a collar on the seating member into contact with an adjacent face on the body part.

When the diaphragm c is moved to the right the corresponding movement of the control bar e effects a reduction of the pump output, a suflicient movement of the diaphragm also imparts an opening movement to the closure member 2'. But the latter movement only occurs when the drop of pressure in the chamber 1 of the body part is that corresponding to an idling speed of the engine, or a high speed under light load. When the closure member is opened it admits a restricted inflow of air to the said chamber for stabilising the diaphragm c, that is to say to minimise or prevent pulsation of the diaphragm. This inflow is accompanied by a drop of air pressure in the compartment n from which air flows into the valve, and the then preponderating air pressure in the compartment m acting on the diaphragm k imparts a followup movement to the seating member for automatically restricting the air inflow to the amount required for enabling an optimum stabilising action to be obtained.

In the modified construction shown in Figure 2, the seating for the closure member i of the air-bleed valve is provided at a position within the bore of the seating member h, and the adjacent end of the said member is closed by a hollow plug q having therein a restricted orifice r leading to the compartment I2.

The seating member 11 is attached to and is movable by the diaphragm k as above described. The other compartment m is in free communication withthe atmosphere through an orifice s and also with the compartment n by way of a port I which is controlled by axial movement of the closure member 11.

In this example the seating member has formed in it passages u leading from the chamber f to the closure member. If desired a similar construction may be used in the arrangement shown in Figure 1. Further instead of shaping the head of the closure member as shown, it may have formed on it a conical head adapted to form with the seating member an annular air aperture of gradually increasing area when the closure member is moved to its open position.

The arrangement shown in Figure 2 is such that when the valve is opened by the diaphragm 0, air can flow therethrough to the chamber 1 in the body part, and as a consequence of the relatively low pressure in the said chamber, air is withdrawn from the compartment )1 which communicates with the valve through the restricted orifice r. The preponderating air pressure in the other compartment m then causes the associated diaphragm k to impart the desired follow-up movement to the closure member, which movement may also restrict or interrupt the air infiow through the port t above mentioned.

The invention is not, however, limited to the examples above described as details of construction or arrangement may be varied to suit different requirements. Further, whilst it is usually more convenient to employ diaphragms for actuating the closure and seating members, equivaient p istgns slidable in cylindrical bores may be used if desire Having thus described my invention what I claim as new and desire to secure by Letters Patent is:

Control means for a liquid fuel injection pump, comprising the combination with a member for regulating the output of the pump, of a hollow body forming a suction chamber and a second chamber at one end or" the suction chamber, a spring-loaded pressure responsive member closing the other end of the suction chamber and connected to the output-regulating member of the pump, a valve having an axially slidable closure member which is operable by the pressure responsive member to admit a restricted flow of stabilising air to the suction chamber when the degree of suction in the suction chamber is sufiiciently high, and also having a seating member which is slidable in a bore in the end of the suction chamber remote from the pressure responsive member, and a second pressure responsive member to which said seating member is secured, and which divides the second chamber into two compartments, the valve being arranged to control communication betwen the suction chamber and at least one of the compartments, and the latter being in communication with the outer atmosphere through orifices at least one of which is restricted, so that when the valve closure member is moved to its open position by the first mentioned pressure responsive member a follow up movement is imparted to the valve seating by a diiierential air pressure acting on the second pressure responsive member.

References Cited in the file of this patent FOREIGN PATENTS 205,291 Switzerland Aug. 14, 1937 

